1. Field of the Invention
The present invention relates to an apparatus and a program for analyzing the time and space variations of an electromagnetic field (electromagnetic wave) in an object. In addition, the present invention also relates to a computer-readable medium storing such a program.
2. Description of the Related Art
Conventionally, various techniques including the finite element method are used for numerically analyzing interactions between substances and electromagnetic fields such as light and radio waves. In particular, recently, an analytical technique called FDTD (finite-difference time-domain) has been receiving attention. According to FDTD, the space is discretized into discrete grid points, and the time variations of electric and magnetic fields at the discrete points are analyzed in accordance with the Maxwell equations.
The modeling of objects under analysis in accordance with FDTD has high degree of freedom. However, in order to obtain accurate analytic results, it is necessary to perform the analysis by using a model of an object which is as close as possible to the real object. Conventionally, the shapes of the calculation models have been defined by combining and arranging simple geometrical elements basically including planes, rectangular parallelepipeds, spheres, cylinders, cones, and the like. In practice, the shapes are defined by using CAD (computer-aided design), and material parameters such as the refractive index and the dielectric constant are assigned to the defined shapes.
In order to input as a calculation model having a shape as close as possible to the shape of the actual object by using the above technique, bothersome input operations are required. For example, the bothersome input operations include operations for input of the shape while observing an electronic image or the like and operations for conversion from the scale of the electronic image to the scale of the coordinate system of the analytical space in the simulation. That is, conventionally, much labor is required for setting the calculation model. According to a proposed technique of FDTD analysis, an electronic image obtained by an optical or electron microscope is directly inputted, and material parameters such as the refractive index and the dielectric constant are set according to the concentration at each pixel of the electronic image. (For example, see Japanese Unexamined Patent Publication No. 2004-279292.) According to this technique, it is possible to accurately reflect the shape of the real object in the calculation model without being limited by geometrical elements which are prepared in advance, and reduce the man-hours required for setting the calculation model.
However, the above technique, in which the material parameters are set according to the concentration at each pixel of the electronic image, cannot produce a calculation model of an object in which particles are randomly distributed and which has a complex distribution of the refractive index.